Making a home made fume a Hood

Vitriodor · Thu Apr 07, 2005 2:29 am

This booklet has been developed to serve as an aid in
selecting a laboratory fume hood ventilation system.
The information is intended to be unbiased and
generic in nature, compiled with help from experienced
architects, laboratory consultants, engineers
and laboratory hood users. The basic understanding
of hood systems you gain from reviewing this booklet
should prove valuable to you as you discuss your
needs with safety officers, engineers and hood
manufacturers.

http://rapidshare.de/files/1159995/Laboratory_hood_system.pdf.html

THE MOON RULES --1 · voted for the moon

icecool · Insistent Chemist

After reading those pdf's you guys posted and reading around a lot I started making an drawing of what my fumehood would need to look like etc.
And I made it out of 4mm thick plexiglass and used silicone kit to hold it together and also used aluminium profiles on the corners of the hood.

Here are pictures of what it has become.

This is the front

This is the side.

This is blacklight for TLC, and it looks funny.

There is a panel that can move up and down it still needs a handel to it to be attached and something has to be made so the panel can be put in different stands.

The ventilator is spark-free and sucks 180 m3/h.

demorol · Fri Apr 15, 2005 10:51 pm

Isn't 4mm plexiglass too thin for such purpose. I'd use at least 8mm thick plexi if I intended to build one myself. You might also consider puting some kind of tubing over the fan, so the fumes would go outside instead all over the room. Othewise it is a nice project.

IndoleAmine · Dreamreader Deluxe

Without tubing a fumehood doesn't make much sense.. Shocked

And the main purpose of fumehoods is to protect the chemist from noxious gasses and fumes, not to function as a detonation protection device - if you plan to let things explode on a regular basis, you can of course install a blast shield at any time, even inside your fumehood. Simply construct a cage of stong wired, narrow steel mesh inside it, or even better something made from sheet steel and welded together, with some holes drilled into it where you need it.. Idea

The professional, several thousdand bucks expensive fumehoods at university are made of 4mm plexiglass, btw. Others I've seen are made from glass. Do you think it would protect one from any explosion happening inside it?

BTW: good job icecool, looks kinda professional! Very Happy

i_a

icecool · Insistent Chemist

Well DOH, of course there is going to be a tube on top of the ventilator it isn't finished yet, also there is no handle on the panel that can move up and down the white TL tube still has to be put in there etc.
But it isn't intended to be bullet/explosion proof.
And any idea what 8mm plexiglass would cost! Shocked

4mmx100cmx100cm costs 59 euro! And I used 4 times 100x100cm plate so that would be 236 euro for only this one ( I didn't pay that price but normally you would).
And a 1,8mm thick plate costs 13 euro for 100x100cm.
4mm is 2 times as thick and costs 4,5 times as expensive. so that would be for 8mm also 4,5 times as expensive that would be 1062 euro for the whole fumehood ONLY on plexiglass....

IndoleAmine · Dreamreader Deluxe

Probably expensive enough to justify the price of commerically available fume hoods. Laughing

Besides, 8mm thickness are as explosion proof as 4mm when it comes to plexiglass, so I would choose the cheaper variant here.

i_a

icecool · Insistent Chemist

I did choose 4mm since 1,8mm is quite flexible and not easy to handle.
Do keep in mind you can't JUST build a fumehood.
There are a lot of problems that you will encounter for example how are you going to saw the plexiglass if you use a big saw the plexiglass will break because of the very crude blade.
And if you use an electric saw (dunno how you call it in english) it will get so hot that the plexiglass will melt again when you passed that piece.

thenewrunne · Chemically Balanced

The fume hood looks great! Sleek design... you have pride in your work for sure.

What sort of bubbler or filter is best for containing solvent smells? Xylene, toulene? Is a charcoal filter the best?

icecool · Insistent Chemist

I thought an active charcoal filter works fine.

bee · Mon Apr 18, 2005 7:59 am

what you guys think 'bout using a "pool light" as a sparkless source of light?

its easy to find (at least for swib)

icecool · Insistent Chemist

What about a TL tube behind a plexiglass plate since there have to be plates in the fumehood anyway that are a bit bent to maintain a bistable vortex inside.
I chose to make a bistable vortex insted of a monostable vortex because if you have a monostable vortex and you open the fumehood slide panel then gasses/fumes can escape threw the opening where the fumehood should suppose to suck air from.

bio · Working Bee

Tested a few Class Ultimate (forget right now) fume hoods in a Chemical Agents Demilitarization Facility. They grid off the opening with string and test the air velocity at different openings of the sash. Then the face and bypass dampers are adjusted accordingly to achieve 5% tolerance over entire opening. Takes a long time then a smoke bomb is used also.

Lacking any instruments what is easily done is to generate some smoke (cigarette)
when doing this. You will find as the sash is opened little by little that the flow deteriorates as the opening increases. At least do this as you may find a spot where the flow is inadequate. Then you know not to open any more than this when doing particularly nasty procedures.

Search for ASHRAE fume hoods standards and you can download a fume hood design and testing manual for air flow versus opening and face & bypass damper design.

A bilge fan for boats is a good economical choice as they are designed to vent gasoline fumes and deliver rating through a 4inch or so hose of a few feet. Mount the fan directly on the box with a discharge pipe as short as possible and not exceeding the manufacturers specs.

Also contrary to popular opinion "explosion proof" NEMA rated equipment is not intended or designed to necessarily be sparkless but rather to contain an explosion if it occurs. For sparkless "intrinsically safe" apparatus is needed. NEMA 4 weatherproof boxes are much cheaper and have full gasketing with threaded hubs (teflon tape here) if you need to do any internal wiring. They are designed to take a 60PSI stream from a 1" hose w/o leaking and actually have better sealing than the "explosion proof" boxes.

Unit you built looks good and should work well given consideration to the above.

icecool · Insistent Chemist

I have been looking for a bilge pump the cheapest one was 194 euro.
And compared to my sparkfree fumehood that is 17 euro's for mine and 194 euro for a bilge pump.
I've got a 7 meter tube attached of 125mm wide to the ventilator and the fumes are carried outside easily.
The diameter of the ventilator (fan) is 120mm.

IndoleAmine · Dreamreader Deluxe

A very good way of testing your fumehood is lighting the contents of a completely filled big ashtray inside the fume cabinet, and watch it burn down completely from the outside, with hood door closed..

If you smell that nasty "ashtray's in fire"-smell every smoker knows, your fumehood is inefficient....

Very Happy